This application claims the priority of Japanese Patent Applications Nos. 11-54295,11-54296, 11-54297, filed on Mar. 2. 1999, No. 11-60993 filed on Mar. 9, 1999, which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a manual and electric motor operated apparatus for lens barrels, and more particularly to an apparatus permitting both manual and electric operations without deliberate switching in driving the zooming and focusing functions of the lens unit.
2. Description of the Prior Art
According to the prior art, a lens barrel for use in photographic cameras or television cameras is provided with a focusing lens for focusing and/or a zoom lens for varying the rate of magnification, and permits switching between manual and electric (automatic) operation modes (e.g. Japanese Patent No. 2773230).
FIGS. 13(A) and 13(B) illustrate an example of configuration concerning zoom driving in a conventional lens barrel. In FIG. 13(B), the left side of a barrel 1 in the drawing is its front side, and the barrel 1 is provided with a zooming ring 3 which is rotatable relative to a body ring 2. This zooming ring 3 is configured to be movable a zoom lens in the direction of the optical axis by its internal mechanism. Also, on the circumference of this zooming ring 3 are formed external gear 4, and to the body ring 2 are fitted a switching gear 6 and a shaft 6A via a bearing member 5, the shaft 6A being separately formed from the switching gear 6, which pivots on the shaft 6A movably in the axial direction and rotatably.
The above mentioned switching gear 6 has, as illustrated, a first toothed wheel 6B engaging with the shaft gear 8 of a zoom motor 7, and a second tooth wheel 6C moving forward to engage with the external gear 4 of the above mentioned zooming ring 3. Furthermore, a switching knob 10 is provided to switch between manual and electric operating modes by a rotational action, and a drive pin 11, fitted to the underside disk of this switching knob 10, is arranged in a concave portion between the above mentioned first toothed wheel 6B and second toothed wheel 6C.
In the above mentioned configuration, when the switching knob 10 is turned into the position of FIG. 13(A), the mechanism is set for manual operation, and the switching gear 6 moves backward to disengage from the external gear 4 of the zooming ring 3. In this state, therefore, the zooming ring 3 can be manually turned, and this turning drives the,zoom lens to a desired rate of magnification.
On the other hand, as the switching knob 10 is turned clockwise from the state of FIG. 13(A), the mechanism is switched to electric (automatic) operation. This switching knob 10, by the turning of its drive pin 11 to the position of the chain line in the drawing, moves the switching gear 6 forward, and engages the second toothed wheel 6C with the above mentioned external gear 4. At this time, the other first toothed wheel 6B does not disengage from the shaft gear 8 of the zoom motor 7. Therefore, when in electric operation, pressing a zooming switch (not shown) turns the zoom motor 7, and this in turn causes the zooming ring 3 to be rotated via the switching gear 6, with the result that the zoom lens is enabled to be driven in a prescribed direction.
However, the above mentioned lens barrel, which can be switched between manual and automatic operation modes, requires a manual switching action to turn the switching knob 10 as stated above, and this action is troublesome. Moreover, this switching action may prevent, for instance, quick focusing on the object to deprive the photographer of a good shooting opportunity.
Also, since the optimal level of heaviness (operation torque) of manipulating the zooming ring 3 as described above may vary with the manual power or preference of the photographer, making it variable as desired would improve the handling case of the camera.
There is the further problem that the level of heaviness (operation torque) of manipulating the zooming ring 3 may vary with the type of the lens and/or other conditions. Thus in such an apparatus, which allows replacement of one type of lens barrel with another, or where various lens barrels are to be fabricated with different lenses built into them, lens barrels even of the same type may vary from one another in fine details, and if they do, the lens driving torque will vary from barrel to barrel. Moreover, the torque may subtly vary with a number of conditions including the ambient temperature and how grease is applied. Such fluctuations in driving torque would pose little problem in electric operation, but in manual operation they would be sensed as differences in actual operation torque.
Furthermore, in an apparatus having a conventional zooming function, a so-called pumping phenomenon, i.e. a change in the angle of field, theretofore occurs when the focusing lens is moved. Thus, in this phenomenon which is more conspicuous at the wide angle end, focusing may invite, for instance, narrowing of the angle of field, therefore resulting in a slightly expanded image.
The present invention has been attempted in view of the problems noted above, and its first object is to provide a manual and electric motor operated apparatus for lens barrels which can dispense with deliberate switching between manual and automatic modes and allow quick adjustment of conditions regarding a given object.
A second object is to enable the torque of manual operation to be freely set for the apparatus which requires no deliberate switching between and manual and automatic modes, and a third object is to prevent the operating torque from being varied by the type of lens and/or other conditions.
A fourth object is to enable the apparatus which requires no deliberate switching between and manual and automatic modes to correct any pumping phenomenon that may arise during a focusing action.
In order to attain the above mentioned first object, a manual and electric motor operated apparatus for lens barrels comprising: a lens barrel for holding lenses movably; an electric motor for automatically moving the lenses; a lens operating ring (manually operating ring), arranged rotatably on the circumference of these lenses for manually moving the lenses, having external gear formed thereon to engage with a transmission gear for transmitting the revolutions of the electric motor; a clutch mechanism for connecting and disconnecting the external gear of this lens operating ring and the electric motor to and from one another; and a clutch operating motor for connecting and disconnecting this clutch mechanism.
The clutch mechanism may have a gear moving plate (clutch disk) which is moved by the above mentioned clutch operating motor in the axial direction and has a gearing function and a gear fixing plate (clutch disk) which is connected to the gear moving plate and has a gearing function, wherein one of these gears is connected to the electric motor side and the other is connected to the external gear of the lens operating ring; and a revolving-while-declutched mechanism for enabling the gear (clutch disk) connected to the external gear of the lens operating ring to rotate when the clutch mechanism is disconnected.
Further, it is preferable to execute an action to connect the clutch mechanism when an operation control signal is supplied from an electric operation switch And to execute an action to disconnect the clutch mechanism when the operation control signal is no longer supplied.
The above mentioned configuration, in which the clutch mechanism is disconnected during manually operation, can drive the zoom lens and the focusing lens by turning the lens operating ring. In that state, the gear moving (or fixing) plate connected to the external gear of the lens operating ring is allowed by the revolving-while-declutched mechanism to turn freely, and accordingly imposes no operational load on the lens operating ring. On the other hand, when the electric operation switch for zooming and focusing is pressed, the clutch operating motor actuates the clutch mechanism and causes the gear moving plate to be connected to the gear fixing plate, so that revolutions by the electric motor are transmitted to the lens operating ring via a gear train and a prescribed lens is thereby driven. If, then, the electric operation switch is released, the connection of the clutch mechanism is released to place the apparatus in a state of standby by for manual operation.
In order to attain the second object mentioned above, according to another aspect of the invention, there is provided an operation torque varying unit using the above mentioned clutch operating motor to adjust the pressing force of the frictional face of the clutch mechanism during the disconnecting action and thereby vary the manual operation torque of the lens operating ring. Where this configuration is used, as stated above with reference to the first aspect of the invention, when the electric operation switch for zooming and focusing is released, the connection of the clutch mechanism is released to place the apparatus in a state of standby for manual operation, and in this state the above mentioned operation torque varying unit causes the pressing force of the frictional face of the clutch mechanism to be adjusted to any desired level designated with a volume control device or the like. Therefore, operation torque given in the above mentioned state of pressing the frictional face is provided to the lens operating ring, enabling the operator to perform manual operation with any operation torque set as desired.
In order to achieve the third object mentioned above, according to another aspect of the invention, there is provided an apparatus comprising a torque detecting circuit for detecting the drive torque for the above mentioned lenses at the time of driving by the electric motor, and an operation torque setting unit for providing a manual operation torque to the lens operating ring by using the clutch operating motor to cause the clutch mechanism, when it is disconnected, to generate its frictional force and maintaining and setting the manual operation torque at a prescribed level by adjusting the above mentioned frictional force on the basis of the output of the torque detecting circuit.
According to this other aspect of the invention, the torque detecting circuit detects the drive torque for the lenses from, for instance the drive current for the electric motor, and the operation torque setting unit, referencing this drive torque level, controls the frictional force if the clutch mechanism, i.e. the slip torque in the clutch mechanism. When the drive torque has been made heavier by, for instance, a lens change, the slip torque is alleviated and when, conversely, the drive torque has become lighter, the slip torque is increased thereby to keep the operation torque constant.
In order to achieve the fourth object stated above, according to another aspect of the invention, there is provided an apparatus comprising an electric motor for automatically moving a zoom lens arranged in a lens barrel; a zooming ring arranged rotatably on the circumference of the lens barrel, for manually moving the zoom lens; a clutch mechanism for connecting and disconnecting the zooming ring and the electric motor to and from each other; a clutch operating motor for connecting and disconnecting the clutch mechanism; and an angle of field correcting unit for connecting, when focusing has been executed when manual zooming is set (during standby for manual operation), the clutch mechanism by using the clutch operating motor and correcting any change in the angle of field due to focusing.
According to this other aspect of the invention, if focusing is done (either manually or electrically) when a state of standby for manual operation has been entered into by disconnecting the clutch mechanism, the clutch mechanism will be connected, and a correction signal, which is calculated on the basis of the set focusing position and a signal of the current zooming position, is supplied to the electric motor. As a result, the zoom lens, for instance, is driven toward the wide angle side to correct the change in the angle of field due to focusing.